Composite film

ABSTRACT

A composite film having a layer structure of at least two layers, wherein a film (A) formed from a ring structure-containing polymer comprising a repeating unit derived from ring-opening or addition polymerization of a monomer having a ring structure, and a film (B) formed from a polycondensation polymer adjoin each other directly or through an adhesive layer.

TECHNICAL FIELD

The present invention relates to composite films and more particularlyto composite films of a multi-layer structure having a film of a polymercontaining a specific ring structure and a film of a polycondensationpolymer. The composite films according to the present invention arehighly balanced among dielectric properties, low water absorptionproperty, mechanical properties, flame retardancy, etc. and are henceparticularly suitable for use as, for example, films for various kindsof wiring boards such as wiring films for semiconductor packages, filmsfor flexible printed wiring boards and wiring films for semiconductormounting.

BACKGROUND ART

With the rapid advancement of advanced information-oriented society inrecent years, development of information processing apparatus such ascomputers and communication apparatus, and image processing apparatussuch as camcoders and digital cameras is being rapidly advanced. In thefield of these electronic apparatus, there is a strong demand for theenhancement of throughput capacity, i.e., the speeding up, andminiaturization and weight saving thereof. In this field, mounting partssuch as semiconductor chips such as LSI, circuit parts and functionalparts are mounted on a wiring board (substrate), and this wiring boardis incorporated into an electronic apparatus. It is effective for thespeeding up of information processing, image processing and the like tomake the interconnected wiring of these mounting parts as short aspossible so as to make the density of the parts high. This technique isalso effective for the miniaturization and weight saving of electronicapparatus.

The use of a flexible substrate made of a synthetic resin film as awiring board itself is effective to realize high-density assembly andthe miniaturization and weight saving of electronic apparatus.Therefore, thin and freely flexible substrates are used in circuitboards such as printed wiring boards.

Even in a mounting system for electronic parts such as semiconductorchips, a system that semiconductor chips are mounted on a wiring boardas bare chips is being developed in place of the conventional mountingsystem by transfer molding. In this mounting system, for example, TAB(tape automated bonding) in which a package itself for LSI is a plasticfilm (including a sheet) is known. TAB is generally formed from atape-like carrier film, bumps (metallic projections) and a semiconductorchip. In such a mounting system, a flexible synthetic resin film havinga wiring pattern is often used as the carrier film.

Polyimide has heretofore been used as a material for substrates offlexible printed wiring boards and films having a wiring pattern.However, a polyimide film is excellent in mechanical properties andflame retardant, but involves a problem that water absorptivity is high.Therefore, the use of the polyimide film as a substrate for high-densityassembly has involved a problem that reliability on insulation islowered due to water absorption, and the dielectric constant of thesubstrate is lowered due to moisture absorption. Accordingly, thepolyimide film cannot be said to be a substrate material sufficientlysatisfying recent high requirements.

On the other hand, ring structure-containing polymers such asring-opening polymers and addition polymers of norbornene monomers suchas tetracyclododecene are publicly known as insulating materialsexcellent in low water absorption property and dielectric properties,and techniques that glass cloth and the like are impregnated with thesepolymers to use them as substrates for printed wiring boards and thatthey are used in the form of a sheet as insulating films have beenproposed (for example, Japanese Patent Application Laid-Open No.248164/1994). However, these ring structure-containing polymers aregenerally insufficient in mechanical strength and flexibility and alsopoor in flame retardant, and so it has been difficult to use them singlyas wiring boards and wiring films.

As described above, there has not been yet found any synthetic resinfilm which has sufficient mechanical strength and flame retardant as afilm for flexible wiring boards and is excellent in low water absorptionproperty and dielectric properties. There is a demand for development ofnovel films highly balanced among these various properties as materialsfor high-density assembly for realizing the speeding up of processingand the miniaturization and weight saving of apparatus.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a composite filmhaving excellent low water absorption property, dielectric properties,mechanical properties and flame retardant and highly balanced amongthese various properties.

Another object of the present invention is to provide a film for wiringboards, which serves for the speeding up of processing and theminiaturization and weight saving of apparatus and has high reliability.

The present inventors have carried out an extensive investigation with aview toward overcoming the above-described problems involved in theprior art, resulting in conceiving composite films having a layerstructure of at least two layers, in which a film (A) formed from a ringstructure-containing polymer such as a thermoplastic norbornene resinand a film (B) formed from a polycondensation polymer such as polyimideadjoin each other directly or through an adhesive layer. When these twokinds of films are combined to form a multi-layer film, a composite filmmaking the best use of their merits can be obtained.

More specifically, when these two kinds of films are combined to form amulti-layer film, a composite film highly balanced between variousproperties such as excellent low water absorption property anddielectric properties that the ring structure-containing polymer film(A) has, and various properties such as excellent mechanical propertiesand flame retardant that the polycondensation polymer film (B) has canbe obtained. When the layer structure is devised, a composite film thata desired property among these various properties is made far excellentcan be obtained.

When it is attempted to form a film of a blend of these two kinds ofsynthetic resins to improve the balance among the above-describedvarious properties, it is necessary to solve a problem thatcompatibility between both resins is poor. In contrast, when filmsrespectively formed from these two kinds of synthetic resins arecombined to form a multi-layer film, the improvement in the variousproperties can be achieved without causing the problem of compatibility.

Upon the formation of the multi-layer film, a composite film can beformed with ease by using a film of one synthetic resin as a support andapplying a solution of the other synthetic resin on to the support toform a film. When the polycondensation polymer is a thermosetting resin,a composite film can be formed by applying a solution of a precursor ofsuch a resin on to the ring structure-containing polymer film (A), andthen heat-treating it to be cured. When the ring structure-containingpolymer contains a hardening agent, a solution containing the ringstructure-containing polymer and the hardening agent can be applied onto a film of the polycondensation polymer and cured. It goes withoutsaying that films of the respective resins may be laminated on eachother to form a composite film. Further, the composite films accordingto the present invention can be used as films for wiring boards such aswiring boards for semiconductor packages, flexible printed wiring boardsand wiring boards for semiconductor chip mounting, since a conductivelayer can be formed on the surfaces thereof.

The present invention has be led to completion on the basis of thesefindings.

According to the present invention, there is thus provided a compositefilm having a layer structure of at least two layers, wherein a film (A)formed from a ring structure-containing polymer comprising a repeatingunit derived from ring-opening or addition polymerization of a monomerhaving a ring structure, and a film (B) formed from a polycondensationpolymer adjoin each other directly or through an adhesive layer.

BEST MODE FOR CARRYING OUT THE INVENTION

Film (A) Formed from Ring Structure-containing Polymer

The film (A) in the present invention is a film formed from a ringstructure-containing polymer comprising a repeating unit derived fromring-opening or addition polymerization of a monomer having a ringstructure. The ring structure-containing polymer may contain variouskinds of compounding additives such as hardening agents, flameretardants, stabilizers, fillers and other synthetic resins as needed.

(Polymer)

The “ring structure-containing polymer comprising a repeating unitderived from ring-opening or addition polymerization of a monomer havinga ring structure” useful in the practice of the present invention is ahomopolymer or copolymer containing a ring structure in its main chainand/or side chain and is preferably a polymer containing a ringstructure in its main chain from the viewpoints of mechanical strength,heat resistance and the like. Examples of the ring structure includearomatic ring structures, saturated cyclic hydrocarbons (cycloalkanes)structures, unsaturated cyclic hydrocarbons (cycloalkenes) structures,etc. Among these, the cycloalkane structures are particularly preferredfrom the viewpoints of mechanical strength, heat resistance and thelike. Accordingly, when the ring structure is an aromatic ring orunsaturated cyclic hydrocarbon, a hydrogenation reaction is preferablyconducted after the polymerization of monomer(s) to convert such astructure into a cycloalkane structure.

Examples of the ring structure include monocycles, polycycles, fusedpolycycles, bridged rings and polycycles composed of these combinations.No particular limitation is imposed on the number of carbon atomsforming the ring structure. However, it is generally preferred that thenumber be within a range of 4 to 30, preferably 5 to 20, more preferably5 to 15, since the properties of mechanical strength, heat resistanceand moldability of the resulting polymer are balanced at a high level.

The bonding style of the monomer having a ring structure is ring-openingpolymerization or addition polymerization. As examples of the ringstructure-containing polymer, may be mentioned:

(a) ring-opening or addition (co)polymers of norbornene monomers havinga norbornene ring, such as norbornene and derivatives thereof,tetracyclododecene and derivatives thereof, and cyclopentadiene andderivatives thereof;

(b) addition (co)polymers of monocyclic cycloolefin monomers such ascyclopentene and cyclohexene;

(c) addition (co)polymers of cyclic conjugated diene monomers such ascyclopentadiene and cyclohexadiene by addition at a 1,3- or1,4-position;

(d) addition (co)polymers of vinyl cyclic hydrocarbons such asvinylcyclohexene, vinylcyclohexane and styrene; and

(e) modified products of these (co)polymers.

As examples of the ring-opening or addition (co)polymers (a) of thenorbornene monomers, may be mentioned:

(1) ring-opening (co)polymers of the norbornene monomers;

(2) addition (co)polymers of the norbornene monomers; and

(3) addition copolymers of the norbornene monomer with another monomer(for example, α-olefin) copolymerizable with the norbornene monomer.

Examples of the modified products (e) of the (co)polymers, may bementioned those obtained by respectively modifying the polymers (a) to(d) by a modification reaction selected from the group consisting of:

{circle around (1)} a hydrogenation reaction of carbon-carbonunsaturated bonds;

{circle around (2)} a graft reaction of a functional group-containingunsaturated compound;

{circle around (3)} a reaction for introducing a functional group bydirect modification of a carbon-carbon unsaturated bond; and

{circle around (4)} combinations of these reactions.

In the present invention, the “repeating unit derived from ring-openingor addition polymerization of a monomer having a ring structure” alsoincludes repeating units modified by a hydrogenation reaction, a graftreaction or the like after polymerization.

These ring structure-containing polymers may be used either singly or inany combination thereof.

Among these ring structure-containing polymers, those having excellentbalance between heat resistance and film-forming property (particularly,flexibility) are preferred. As the ring structure-containing polymershaving such excellent properties, are preferred the ring-opening(co)polymers and addition (co)polymers of the norbornene monomers, andmodified products thereof. Thermoplastic norbornene resins such as thesenorbornene polymers and modified products thereof are also excellent inmechanical strength, molding and processing ability, etc.

The ring structure-containing polymers desirably contain the repeatingunit derived from the monomer having a ring structure in a proportion ofgenerally at least 50 mol %, preferably at least 70 mol %, morepreferably at least 80 mol % based on the whole repeating unit of thepolymer.

When a monomer having an organic group having two or more carbon atomsin a side chain is used as the monomer having a ring structure eithersingly or in combination with another monomer having a ring structure, aring structure-containing polymer film excellent in flexibility,adhesion property to metals, etc. can be obtained. Examples of such anorganic group include hydrocarbon groups, oxygen-containing organicgroups, nitrogen-containing organic groups, etc. The organic grouphaving two or more carbon atoms is preferably a hydrocarbon group having2 to 20 carbon atoms, and examples thereof include alkyl and alkylidenegroups such as ethyl, ethylidene, propylene, butyl, pentyl, hexyl,octyl, decyl, butylidene, pentylidene, hexylidene and decylidene groups.Among these groups, linear alkyl groups are preferred. The number ofcarbon atoms in the organic group is preferably 4 to 20 atoms, morepreferably 6 to 12 atoms.

The proportion of the “monomer having an organic group having two ormore carbon atoms in a side chain”0 in the monomer(s) having a ringstructure is within a range of preferably 5 to 100 mol %, morepreferably 10 to 70 mol %. Specific examples of such a ringstructure-containing polymer include ring-opening polymers ofethyltetracyclododecene and ethylidenetetracyclododecene, additioncopolymers of norbornene and decylnorbornene, addition copolymers ofnorbornene and hexylnorbornene, and modified product thereof.

(Monomer Having a Ring Structure)

The monomer having a ring structure used in the present invention willhereinafter be described more specifically.

(i) Norbornene Monomer

The norbornene monomer used in the present invention is a alicyclicmonomer having a norbornene ring, which is described in, for example,Japanese Patent Application Laid-Open Nos. 320268/1993 and 36224/1990.Typical examples thereof include monomers having no other unsaturatedbond than a carbon-carbon unsaturated bond participating in apolymerization reaction, such as norbornene, tetracyclododecene andalkyl-substituted products thereof; monomers having another unsaturatedbond in addition to a carbon-carbon unsaturated bond participating in apolymerization reaction, such as ethylidenenorbornene, vinylnorbornene,ethylidenetetracyclododecene and dicyclopentadiene; monomers having anaromatic ring, such as dimethanotetrahydrofluorene and phenylnorbornene;and monomers having a functional group (particularly, a polar group),such as methoxycarbonylnorbornene and methoxycarbonyltetracyclododecene.

Specific examples of the monomer having no other unsaturated bond than acarbon-carbon unsaturated bond participating in a polymerizationreaction include bicyclo[2.2.1]hept-2-ene derivatives such asbicyclo[2.2.1]hept-2-ene (i.e. norbornene),5-methylbicyclo[2.2.1]hept-2-ene, 5-ethylbicyclo[2.2.1]hept-2-ene,5-butylbicyclo[2.2.1]hept-2-ene, 5-hexylbicyclo[2.2.1]hept-2-ene and5-decylbicyclo[2.2.1]hept-2-ene; tetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene derivatives such astetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene (i.e.tetracyclododecene),8-methyltetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene and8-ethyltetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene;tricyclo[4.3.1^(2,5).0]-dec-3-ene; and bicyclo[2.2.1]hept-2-enederivatives having a cyclic substituent group, such as5-cyclohexylbicyclo[2.2.1]hept-2-ene and5-cyclopentyl-bicyclo[2.2.1]hept-2-ene.

Specific examples of the monomer having another unsaturated bond inaddition to a carbon-carbon unsaturated bond participating in apolymerization reaction include bicyclo[2.2.1]hept-2-ene derivativeshaving an unsaturated bond outside its ring, such as5-ethylidenebicyclo[2.2.1]hept-2-ene, 5-vinylbicyclo[2.2.1]hept-2-eneand 5-propenylbicyclo[2.2.1]hept-2-ene;tetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene derivatives having anunsaturated bond outside its ring, such as8-methylidenetetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene,8-ethylidenetetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene,8-vinyltetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene and8-propenyltetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene;tricyclo-[4.3.1^(2,5).0]-dec-3,7-diene; and bicyclo[2.2.1]hept-2-enederivatives having a cyclic substituent group with an unsaturated bond,such as 5-cyclohexenylbicyclo[2.2.1]hept-2-ene and5-cyclopentenylbicyclo[2.2.1]hept-2-ene.

Specific examples of the monomer having an aromatic ring include5-phenylbicyclo[2.2.1]hept-2-ene,tetracyclo[6.5.1^(2,5).0^(1,6).0^(8,13)]tridec-3,8,10,12-tetraene (alsoreferred to as 1,4-methano-1,4,4a,9a-tetrahydrofluorene) andtetracyclo[6.6.1^(2,5).0^(1,6).0^(8,13)]tetradec-3,8,10,12-tetraene(also referred to as 1,4-methano-1,4,4a,5,10,10a-hexahydroanthracene).

Specific examples of the monomer having a functional group (especially,polar group) include bicyclo[2.2.1]hept-2-ene derivatives having atleast one substituent group containing an oxygen atom, such as5-methoxycarbonylbicyclo[2.2.1]hept-2-ene,5-ethoxycarbonylbicyclo[2.2.1]hept-2-ene,5-methyl-5-methoxycarbonylbicyclo[2.2.1]hept-2-ene,5-methyl-5-ethoxycarbonylbicyclo[2.2.1]hept-2-ene,bicyclo[2.2.1]hept-5-enyl-2-methylpropionate,bicyclo[2.2.1]hept-5-enyl-2-methyloctanoate,bicyclo[2.2.1]hept-2-ene-5,6-dicarboxylic acid anhydride,5-hydroxymethylbicyclo[2.2.1]hept-2-ene,5,6-di(hydroxymethyl)bicyclo[2.2.1]hept-2-ene,5-hydroxyisopropylbicyclo[2.2.1]hept-2-ene and5,6-dicarboxybicyclo[2.2.1]hept-2-ene;tetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene derivatives having atleast one substituent group containing an oxygen atom, such as8-methoxycarbonyltetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene,8-methyl-8-methoxycarbonyltetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene,8-hydroxymethyltetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene and8-carboxytetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene; andbicyclo[2.2.1]hept-2-ene derivatives having at least one substituentgroup containing a nitrogen atom, such as5-cyanobicyclo[2.2.1]hept-2-ene andbicyclo[2.2.1]hept-2-ene-5,6-dicarboxylic acid imide.

In addition, in all the above-mentioned norbornene monomers in common,there may be mentioned norbornene monomers having an organic grouphaving two or more, preferably four or more carbon atoms, preferably ahydrocarbon group, more preferably an alkyl group as a substituentgroup.

These norbornene monomers can be subjected to ring-opening(co)polymerization or addition (co)polymerization in accordance with amethod known per se in the art. In addition, these norbornene monomersmay be subjected to addition copolymerization with another monomer (forexample, an α-olefin which will be described subsequently)copolymerizable therewith.

(ii) Monocyclic Cycloolefin Monomer

The monocyclic cycloolefin monomer is a cyclic compound having acarbon-carbon double bond in its ring. Specific examples thereof includecyclobutene, cyclopentene, cyclohexene, cycloheptene, cycyclooctene andsubstituted derivatives (for example, alkyl-substituted products andpolar group-substituted products) thereof (for example, Japanese PatentApplication Laid-Open No. 66216/1989). These monocyclic cycloolefinmonomers may be used either singly or in any combination thereof.

(iii) Cyclic Conjugated Diene Monomer

The cyclic conjugated diene monomer is a cyclic compound havingconjugated carbon-carbon double bonds in its ring. Specific examplesthereof include 1,3-cyclopentadiene, 1,3-cyclohexadiene,1,3-cycloheptadiene, 1,3-cyclooctadiene and substituted derivatives (forexample, alkyl-substituted products and polar group-substitutedproducts) thereof (for example, Japanese Patent Application Laid-OpenNos. 136057/1994 and 258318/1995). These cyclic conjugated dienemonomers can be polymerized in accordance with a publicly known processto obtain 1,3- or 1,4-addition (co)polymers. These cyclic conjugateddiene monomers may be used either singly on in any combination thereof.

(iv) Vinyl Cyclic Hydrocarbon Monomer

Examples of the vinyl cyclic hydrocarbon monomer include vinyl cyclichydrocarbons such as vinylcyclopentene, vinylcyclopentane,vinylcyclohexene, vinylcyclohexane, vinylcycloheptene,vinylcycloheptane, vinylcyclooctene, vinylcyclooctane and substitutedderivatives (for example, alkyl-substituted products and polargroup-substituted products) thereof (for example, Japanese PatentApplication Laid-Open No. 59989/1976). In addition, aromatic vinylmonomers such as styrene and α-methylstyrene may also be mentioned.These monomers may be addition-(co)polymerized in accordance with amethod known per se in the art. When an unsaturated bond is contained inthe ring, the resulting polymer is preferably hydrogenated afterpolymerization.

Among these, the ring structure is preferably a 5- to 7-membered ringfrom the viewpoint of balance among heat resistance, moldability andstrength properties, with vinylcyclohexene polymers, vinylcyclohexanepolymers or hydrogenated products thereof, and aromatic vinyl polymersor hydrogenated products thereof being most preferred.

(v) Copolymerizable Another Monomer

In the present invention, the monomer having a ring structure may besubjected to addition (co)polymerization with another monomercopolymerizable therewith as needed.

Examples of another monomer include α-olefins having 2 to 12 carbonatoms, such as ethylene, propylene, 1-butene, 4-methyl-1-pentene; linearconjugated dienes such as 1,3-butadiene and isoprene; vinyl ethers suchas ethyl vinyl ether and isobutyl vinyl ether; and carbon monoxide. Acopolymer obtained by using the α-olefin among these toaddition-copolymerize it with the norbornene monomer is preferred as thering structure-containing polymer.

(Modified Product)

As the ring structure-containing polymer useful in the practice of thepresent invention, the ring-opening or addition (co)polymer of themonomer having a ring structure may be used as it is. When anunsaturated bond is present in the main chain, side chain or ringstructure thereof, however, it is preferred to conduct a hydrogenationreaction to saturate it from the viewpoint of heat stability andlong-term reliability. The ring-structure-containing polymer ispreferably that into which a functional group has been introduced forthe purpose of improving the adhesion property to a conductive layer(wiring layer) on a film (A) formed thereof and the film (B). Bothhydrogenation and introduction of the functional group may be conducted.

The hydrogenated product can be obtained by hydrogenating thering-opening or addition (co)polymer of the monomer having a ringstructure with hydrogen in the presence of a hydrogenation catalyst inaccordance with a method known per se in the art. The carbon-carbonunsaturated bond present in the main chain or side chain is partially orwholly hydrogenated with hydrogen to saturate it. When the polymer hasan aromatic ring, the aromatic ring may be hydrogenated byhydrogenation. In the case of a norbornene polymer having an aromaticring, only unsaturated bonds in the main chain and side chain may behydrogenated to retain the aromatic ring as it is.

As the functional group introduced into the ring-opening or addition(co)polymer of the monomer having a ring structure, is preferred afunctional group (polar group) composed of an organic group having aheteroatom and having a polarity. Examples of the heteroatom includeoxygen, nitrogen, sulfur, silicon and halogens. Polar groups having anoxygen or nitrogen atom is preferred from the viewpoints of adhesionproperty and reactivity.

The ring structure-containing polymer used in the present invention maybe formed into a film to combine it with the film (B) of thepolycondensation polymer, and a conductive layer (wiring layer) may befurther formed thereon. The ring structure-containing polymer may beprovided as a curable resin by containing a hardening agent therein.Therefore, the polar group introduced is preferably such a polar groupas improves the adhesion property to mainly the wiring layer and thefilm (B) or has a function of serving as a hardening site upon hardeningreaction.

Specific example of the functional group include epoxy, carboxyl,hydroxyl, ester, silanol, silyl, amino, nitrile, halogeno, acyl, sulfoneand vinyl groups.

Of these, oxygen-containing functional groups capable of reacting withan acid or basic hardening agent such as a polyhydric phenol or amine,for example, polar groups such as epoxy, acid anhydride, carboxyl andhydroxyl groups are preferred for reasons of, for example, (1) making itpossible to enhance crosslinking density and adhesion property at a lowmodification rate, (2) permitting the selection of a hardening agentfrom a wide range, and (3) easily controlling a curing rate with thehardening agent, with functional groups which generate a terminal-OHgroup such as a hydroxyl or carboxyl group after curing, for example,epoxy and acid anhydride groups being particularly preferred. Thesefunctional groups may be used either singly or in any combinationthereof.

The rate of introduction of the functional group is suitably selected asnecessary for the end application intended. However, it is generallywithin a range of 0.1 to 100 mol %, preferably 2 to 80 mol %, morepreferably 5 to 50 mol % based on the whole repeating unit in thepolymer. When the rate of introduction of the functional group in thering structure-containing polymer falls within this range, the adhesionstrength to metals, heat resistance, mechanical strength, waterabsorptivity and dielectric properties of the polymer are balanced withone another at a high level. It is hence preferable to introduce thefunctional group at a rate of introduction within the above range.

Examples of a process for the introduction of the functional groupinclude a process in which a ring-opening or addition (co)polymer of themonomer having a ring structure, or a hydrogenated product thereof ismodified, and a process in which a monomer having a functional group iscopolymerized upon the preparation of the (co)polymer. Specific examplesthereof include (1) a process in which a unsaturated compound having afunctional group is introduced into the ring-opening or addition(co)polymer of the monomer having a ring structure, or a hydrogenatedproduct thereof by a graft reaction (graft modification process), (2) aprocess in which a functional group is directly added to a carbon-carbonunsaturated bond in the (co)polymer or the hydrogenated product thereofwhen the carbon-carbon unsaturated bond is present therein (directmodification process), and (3) a process in which a monomer having afunctional group is copolymerized in advance upon the preparation of the(co)polymer (copolymerization process).

With respect to the case where a polar group is used as the functionalgroup, the respective processes will hereinafter be described in detail.Incidentally, the copolymerization process (3) is not a modificationprocess, but it is described here for the sake of convenience.

(1) Graft Reaction of Polar Group-containing Unsaturated Compound

The introduction of a polar group by the graft modification process canbe conducted by reacting the ring-opening or addition (co)polymer of themonomer having a ring structure, or a hydrogenated product thereof witha polar group-containing unsaturated compound in the presence of aradical generator such as an organic peroxide. No particular limitationis imposed on the polar group-containing unsaturated compound. However,epoxy group-containing unsaturated compounds, carboxyl group-containingunsaturated compounds, hydroxyl group-containing unsaturated compounds,silyl group-containing unsaturated compounds, etc. are preferred becausemaking it is possible to enhance crosslinking density and adhesionproperty to the conductive layer and film (B) at a low modificationrate, and photosensitivity can be imparted as needed.

Examples of the epoxy group-containing unsaturated compounds includeglycidyl esters such as glycidyl acrylate, glycidyl methacrylate andglycidyl p-styrylcarboxylate; mono- or polyglycidyl esters ofunsaturated polycarboxylic acids such asendo-cis-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acid andendo-cis-bicyclo[2,2,1]hept-5-ene-2-methyl-2,3-dicarboxylic acid;unsaturated glycidyl ethers such as allyl glycidyl ether, 2-methylallylglycidyl ether, glycidyl ether of o-allylphenol, glycidyl ether ofm-allylphenol and glycidyl ether of p-allylphenol; and2-(o-vinylphenyl)ethylene oxide, 2-(p-vinylphenyl)ethylene oxide,2-(o-allylphenyl)ethylene oxide, 2-(p-allylphenyl)ethylene oxide,2-(o-vinylphenyl)propylene oxide, 2-(p-vinylphenyl)propylene oxide,2-(o-allylphenyl)propylene oxide, 2-(p-allylphenyl)propylene oxide,p-glycidylstyrene, 3,4-epoxy-1-butene, 3,4-epoxy-3-methyl-1-butene,3,4-epoxy-1-pentene, 3,4-epoxy-3-methyl-1-pentene, 5,6-epoxy-1-hexene,vinylcyclohexene monoxide and allyl-2,3-epoxycyclopentyl ether.

Of these, the allyl glycidyl esters, allyl glycidyl ethers and5,6-epoxy-1-hexene etc. are preferred, with the allyl glycidyl ethersbeing particularly preferred, in that such an epoxy group-containingunsaturated compound permits graft addition at a particularly highreaction rate. These epoxy group-containing unsaturated compounds may beused either singly or in any combination thereof.

As examples of the carboxyl group-containing unsaturated compounds, maybe mentioned compounds described in Japanese Patent ApplicationLaid-Open No. 271356/1993, for example, unsaturated carboxylic acidssuch as acrylic acid, methacrylic acid and α-ethylacrylic acid; andunsaturated dicarboxylic acid such as maleic acid, fumaric acid,itaconic acid, endo-cis-bicyclo-[2.2.1]hept-5-ene-2,3-dicarboxylic acidand methyl-endo-cis-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid. Asexamples of the unsaturated carboxylic acid derivatives, may bementioned anhydrides, esters, halides, amides and imides of unsaturatedcarboxylic acids, and specific examples thereof include acid anhydridessuch as maleic anhydride, chloromaleic anhydride, butenylsuccinicanhydride, tetrahydrophthalic anhydride and citraconic anhydride; esterssuch as monomethyl maleate, dimethyl maleate and glycidyl maleate; andmalenyl chloride and maleimide. Of these, acid anhydrides such as maleicanhydride and itaconic anhydride are particularly preferred for theabove-described reasons.

Examples of the hydroxyl group-containing unsaturated compounds includeallyl alcohol, 2-allyl-6-methoxyphenol,4-allyloxy-2-hydroxybenzophenone, 3-allyloxy-1,2-propanediol,2-allyloxy-phenol, 3-buten-1-ol, 4-penten-1-ol and 5-hexen-1-ol.

Examples of the silyl group-containing unsaturated compounds includechlorodimethylvinylsilane, trimethylsilylacetylene,5-trimethylsilyl-1,3-cyclopentadiene, 3-trimethylsilylallyl alcohol,trimethylsilyl methacrylate, 1-trimethylsilyloxy-1,3-butadiene,1-trimethylsilyloxycyclopentene, 2-trimethylsilyloxyethyl methacrylate,2-trimethylsilyloxyfuran, 2-trimethylsilyloxypropene,allyloxy-t-butyldimethylsilane and allyloxytrimethylsilane.

Unsaturated organosilicon compounds include trisalkoxyvinylsilanes suchas trimethoxyvinylsilane, triethoxyvinylsilane,tris(methoxyethoxy)vinylsilane. The alkoxy groups in such an unsaturatedorganosilicon compounds can be hydrolyzed into silanol groups.

The graft-modified ring structure-containing polymer can be obtained bygraft-reacting the unsaturated compound having a functional group suchas a polar group with the ring-opening or addition (co)polymer of themonomer having a ring structure, or a hydrogenated product thereof undergeneration of a radical. As methods for generating the radical, may bementioned (i) a method making use of an organic peroxide, (ii) a methodmaking use of a photo-induced radical generator, (iii) a method byirradiation of energy rays, and (iv) a method by heating.

As the radical initiator, an organic peroxide is generally used. Theorganic peroxide is preferably the same as that which will be describedsubsequently in the item of the hardening agent. An azo compound mayalso be used as the radical generator. As specific examples of the azocompound, may be mentioned azobisisobutyronitrile and dimethylazoisobutyrate. Of these, dialkyl peroxides are preferably used as theorganic peroxides. These organic peroxides may be used either singly orin any combination thereof.

A proportion of the organic peroxide used is generally within a range of0.001 to 30 parts by weight, preferably 0.01 to 20 parts by weight, morepreferably 0.1 to 15 parts by weight per 100 parts by weight of the(co)polymer or the hydrogenated product thereof in terms of a chargedproportion upon the reaction. When the proportion of the organicperoxide used falls within this range, the rate of reaction of the polargroup-containing unsaturated compound, and various properties of theresulting functional group-containing polymer, such as waterabsorptivity and dielectric properties, are balanced with one another ata high level. It is hence preferable to use the organic peroxide withinsuch a range.

No particular limitation is imposed on the graft-modification reaction,and the reaction may be carried out in accordance with a method knownper se in the art. The reaction is conducted at a temperature ofgenerally 0 to 400° C., preferably 60 to 350° C. The reaction time isgenerally within a range of 1 minute to 24 hours, preferably 30 minutesto 10 hours. After completion of the reaction, a poor solvent such asmethanol is added in a great amount to the reaction system to deposit apolymer formed, and the polymer can be collected by filtration, washedand then dried under reduced pressure.

(2) Direct Modification of Carbon-carbon Unsaturated Bond

Into the ring structure-containing polymer according to the presentinvention, a polar group can be introduced by using carbon-carbonunsaturated bond in the ring-opening or addition (co)polymer of themonomer having a ring structure or the hydrogenated product thereof toadd the polar group thereto or bond a compound having a polar groupthereto.

No particular limitation is imposed on the process for introducing thepolar group. However, an example thereof includes a process in which apolar group such as an epoxy group, carboxyl group or hydroxyl group isintroduced in accordance with any one of (i) a method by oxidation ofunsaturated bonds, (ii) a method by an addition reaction of a compoundcontaining at least one polar group in its molecule to unsaturatedbonds, and (iii) any other method (for example, Japanese PatentApplication Laid-Open No. 172423/1994).

(3) Copolymerization of Polar Group-containing Monomer

No particular limitation is imposed on the functional group-containingmonomer. In the case of a norbornene polymer, however, it is preferredto copolymerize any one of such norbornene monomers having a polar groupsuch as a hydroxyl, carboxyl or ester group as mentioned above as theexamples of the norbornene monomers, for example,5-hydroxymethylnorbornene, 5-hydroxyisopropylnorbornene,5-methoxycarbonylnorbornene, 8-methoxycarbonyltetracyclododecene or5,6-dicarboxynorbornene. With respect to a polymerization catalyst and apolymerization process, publicly known polymerization catalysts andpolymerization processes for norbornene monomers may be used.

Of the above-described processes, the graft-modification process ispreferred as the process for introducing the polar group for reasons of,for example, the fact that the modification can be carried out undereasy reaction conditions and that the functional group can be easilyintroduced at a high modification rate. As the kind of the polargroup-containing unsaturated compound subjected to the graft reaction,is particularly preferred an unsaturated compound having an epoxy groupor an unsaturated compound having a dicarboxylic acid anhydride groupand a carbon-carbon unsaturated bond in its molecule, such as maleicanhydride or itaconic anhydride for the above-described reasons.

The rate of introduction of the functional group in the ringstructure-containing polymer having a functional group used in thepresent invention is suitably selected as necessary for the endapplication intended. However, it is generally within a range of 0.1 to100 mol %, preferably 0.5 to 50 mol %, more preferably 1 to 30 mol %based on the whole repeating unit (the total number of monomer units) inthe polymer. When the rate of introduction of the functional group inthe ring structure-containing polymer falls within this range, thefilm-forming property, strength properties, heat resistance, solventresistance and dielectric properties of the polymer are balanced withone another at a high level. It is hence preferable to introduce thefunctional group at a rate of introduction within the above range.

The rate of introduction of the functional group (modification rate: mol%) is represented by the following equation (1):

Rate of introduction of the functional group=(X/Y)×100  (1)

wherein

X:

(a) the total number of moles of modification residue introduced by agraft monomer,

(b) (the total number of moles of unsaturated bond-containingmonomer)×(rate of addition of functional group to unsaturated bonds), or

(c) the total number of moles of the functional group-containing monomer

(all, determined by ¹H-NMR); and

Y: the total number of monomer units in the polymer (weight averagemolecular weight of the polymer/average molecular weight of themonomer).

(Physical Properties of Ring Structure-containing Polymer)

The molecular weight of the ring structure-containing polymer used inthe present invention is suitably selected as necessary for the endapplication intended, but is generally within a range of 1,000 to1,000,000, preferably 5,000 to 500,000, more preferably 10,000 to250,000, most preferably 2,000 to 200,000 when expressed by a weightaverage molecular weight (Mw) as measured by gel permeationchromatography (GPC) using toluene as a solvent. When the Mw of the ringstructure-containing polymer falls within this range, the mechanicalstrength and flexibility of the polymer are balanced with each other ata high level. It is hence preferable to use a polymer having a molecularweight within such a range.

The molecular weight distribution of the ring structure-containingpolymer used in the present invention is suitably selected as necessaryfor the end application intended. However, it is preferred that itsratio (Mw/Mn) of the weight average molecular weight (Mw) to the numberaverage molecular weight (Mn) as measured by GPC using toluene as asolvent be generally 5.0 or lower, preferably 4.0 or lower, morepreferably 3.0 or lower, since the mechanical strength and flexibilityof the polymer are balanced with each other at a high level.

These ring structure-containing polymers may be used either singly or inany combination thereof.

(Compounding Additives)

The film (A) used in the present invention may be formed by mixingcompounding additives with the ring structure-containing polymer asneeded. More specifically, the ring structure-containing polymer can beused as a resin composition comprising various kinds of additives.Examples of the compounding additives include hardening agents,hardening auxiliaries, flame retardants, stabilizers, fillers and otherresins.

It is particularly preferred that a hardening agent be incorporated intothe ring structure-containing polymer to use the polymer as a curableresin composition for the purpose of improving the heat resistance andstrength properties of the film (A).

Hardening Agent

No particular limitation is imposed on the hardening agent used in thepresent invention, and examples thereof include (1) organic peroxides,(2) hardening agents capable of exhibiting their effect by heat, and (3)hardening agents capable of exhibiting their effect by light.

Besides, hardening agents may also be classified into (i) those (organicperoxides, quinone and quinone dioxime derivatives, azo compound, etc.)which form a radical to develop the effect, and (ii) those (phenolresins, amino resins, halogen compounds, amine compounds, aziridinecompounds, isocyanate compounds, carboxylic acids, acid anhydrides,aldehydes, epoxy compounds, metal oxides, sulfides, metal halides,organometal halides, silane compounds, epoxy resin-hardening agents,etc.) which form an ion as an acid or base to develop the effect. In thepresent specification, specific examples of the hardening agent will bedescribed in more detail in accordance with the former classification.

(1) Organic Peroxide

Examples of the organic peroxide include ketone peroxides such as methylethyl ketone peroxide and cyclohexanone peroxide; peroxyketals such as1,1-bis(t-butyl peroxy)-3,3,5-trimethylcyclohexane and 2,2-bis(t-butylperoxy)butane; hydroperoxides such as t-butyl hydroperoxide and2,5-dimethylhexane-2,5-dihydroperoxide; dialkyl peroxides such asdicumyl peroxide, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexyne-3 andα,α′-bis(t-butyl peroxy-m-isopropyl)benzene; diacyl peroxides such asoctanoyl peroxide and isobutyryl peroxide; and peroxyesters such asperoxydicarbonate. Of these, the dialkyl peroxides are preferred fromthe viewpoint of performance of the crosslinked resin. The kind of thealkyl group can be changed according to the curing temperature (formingor molding temperature).

No particular limitation is imposed on the amount of the organicperoxide blended. However, it is used within a range of generally 0.1 to30 parts by weight, preferably 1 to 20 parts by weight per 100 parts byweight of the ring structure-containing polymer from the viewpoints ofefficiently conducting a crosslinking reaction, improving the physicalproperties of the resulting cured polymer, and being profitable. If theblending amount is too little, the resulting composition becomes hard toundergo crosslinking, and so sufficient heat resistance and solventresistance cannot be imparted to the composition. If the amount is toogreat on the other hand, the properties of the cured resin, such aswater absorption property and dielectric properties are deteriorated. Itis hence not preferred to use the organic peroxide in such a too smallor great amount. The blending amount within the above range is preferredbecause these properties are balanced with each other at a high level.

(2) Hardening Agent Capable of Exhibiting its Effect by Heat

No particular limitation is imposed on the hardening agent capable ofexhibiting its effect by heat so far as it can cause a crosslinkingreaction by heating. However, specific preferable examples thereofinclude aliphatic polyamines, alicyclic polyamines, aromatic polyamines,bisazides, acid anhydrides, dicarboxylic acids, diols, polyhydricphenols, polyamides, diisocyanates and polyisocyanates.

Specific examples thereof include aliphatic polyamines such ashexamethylenediamine, triethylenetetramine, diethylenetriamine andtetraethylenepentamine; alicyclic polyamines such as diaminocyclohexane,3(4),8(9)-bis(aminomethyl)tricyclo[5,2,1,0^(2,6)]decane,1,3-(diaminomethyl)cyclohexane, menthenediamine, isophoronediamine,N-aminoethylpiperazine, bis(4-amino-3-methylcyclohexyl)methane andbis(4-aminocyclohexyl)methane; aromatic polyamines such as4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane,α,α′-bis(4-aminophenyl)-1,3-diisopropylbenzene,α,α′-bis(4-aminophenyl)-1,4-diisopropylbenzene, 4,4′-diaminodiphenylsulfone, m-phenylenediamine and m-xylylenediamine; bisazides such as4,4′-bisazidobenzal(4-methyl)cyclohexanone, 4,4′-diazidochalcone,2,6-bis(4′-azidobenzal)cyclohexanone,2,6-bis(4′-azidobenzal)-4-methylcyclohexanone,4,4′-diazidodiphenylsulfone, 4,4′-diazidodiphenylmethane and2,2′-diazidostilbene; acid anhydrides such as phthalic anhydride,pyromellitic anhydride, benzophenonetetracarboxylic acid anhydride,nadic anhydride, 1,2-cyclohexanedicarboxylic acid, maleicanhydride-modified polypropylene and maleic anhydride-modifiedcycloolefin resins; dicarboxylic acids such as fumaric acid, phthalicacid, maleic acid, trimellitic acid and himic acid; diols such as1,3′-butanediol, 1,4′-butanediol, hydroquinonedihydroxydiethyl ether andtricyclodecanedimethanol; triols such as 1,1,1-trimethylolpropane;polyhydric phenols such as phenol novolak resins and cresol novolakresin; polyamides such as nylon 6, nylon 66, nylon 610, nylon 11, nylon612, nylon 12, nylon 46, methoxymethylated polyamide,polyhexamethylenediamine terephthalamide and polyhexamethyleneisophthalamide; and diisocyanates such as hexamethylene diisocyanate andtuluylene diisocyanate.

These hardening agents may be used either singly or in any combinationthereof. Of these, the aliphatic polyamines and aromatic polyamines arepreferred for reasons of easy uniform dispersion. Further, the aromaticpolyamines from the viewpoint of excellent heat resistance, and thepolyhydric phenols from the viewpoint of excellent strength propertiesare particularly preferred.

No particular limitation is imposed on the amount of the hardening agentblended. From the viewpoints of being able to efficiently conduct acrosslinking reaction and improve the physical properties of theresulting crosslinked resin, and being profitable, however, it isgenerally within a range of 0.1 to 30 parts by weight, preferably 1 to20 parts by weight per 100 parts by weight of the ringstructure-containing polymer. If the amount of the hardening agent istoo little, the resulting composition becomes hard to undergocrosslinking, and so sufficient heat resistance and solvent resistancecannot be imparted to the composition. To the contrary, any amount toogreat results in a crosslinked resin lowered in properties such as waterabsorption property and dielectric properties. It is hence not preferredto use the hardening agent in any amount outside the above range. Theblending amount within the above range is preferred because theseproperties are balanced with each other at a high level.

A hardening accelerator may also be blended, as needed, to enhance theefficiency of the crosslinking reaction. Examples of the hardeningaccelerator include amines such as pyridine, benzyldimethylamine,triethanolamine, triethylamine, tributylamine, tribenzylamine,dimethylformamide and imidazoles. The hardening accelerator is added inorder to regulate curing rate and further enhance the efficiency of thecrosslinking reaction. No particular limitation is imposed on the amountof the hardening accelerator blended. However, it is used within a rangeof generally 0.1 to 30 parts by weight, preferably 1 to 20 parts byweight per 100 parts by weight of the ring structure-containing polymer.The blending amount of the hardening accelerator within this range ispreferred because crosslinking density, dielectric properties, waterabsorptivity and the like of the crosslinked resin are balanced with oneanother at a high level. Among others, imidazoles are preferred in thata cured resin excellent in dielectric properties can be provided.

(3) Hardening Agent Capable of Exhibiting its Effect by Light

No particular limitation is imposed on the hardening agent capable ofexhibiting its effect by light so far as it is a photo-induced hardeningagent which reacts with the ring structure-containing polymer byirradiation of actinic rays such as ultraviolet rays such as g rays, hrays or i rays, far ultraviolet rays, X rays, or electron rays to form acrosslinked compound. However, examples thereof include aromaticbisazide compounds, photo-induced mine generators and photo-induced acidgenerators.

Specific examples of the aromatic bisazide compounds include4,4′-diazidochalcone, 2,6-bis(4′-azidobenzal)-cyclohexanone,2,6-bis(4′-azidobenzal)-4-methylcyclohexanone, 4,4′-diazidodiphenylsulfone, 4,4′-diazidobenzophenone, 4,4′-diazidophenyl,2,7-diazidofluorene and 4,4′-diazidophenylmethane. These compounds maybe used either singly or in any combination thereof.

Specific examples of the photo-induced amine generators includeo-nitrobenzyloxycarbonylcarbamates,2,6-dinitrobenzyloxycarbonylcarbamates andα,α-dimethyl-3,5-dimethoxybenzyloxycarbonylcarbamates of aromatic aminesor aliphatic amines. More specifically, there may be mentionedo-nitrobenzyloxycarbonylcarbamates of aniline, cyclohexylamine,piperidine, hexamethylenediamine, triethylenetetramine,1,3-(diaminomethyl)cyclohexane, 4,4′-diaminodiphenyl ether,4,4′-diaminodiphenylmethane, phenylenediamine and the like. Thesecompounds may be used either singly or in any combination thereof.

The photo-induced acid generator is a substance which forms a Brφnstedacid or Lewis acid upon exposure to actinic rays. Examples thereofinclude onium salts, halogenated organic compounds, quinonediazidecompounds, α,α-bis(sulfonyl)diazomethane compounds,α-carbonyl-α-sulfonyldiazomethane compounds, sulfone compounds, organicacid ester compounds, organic acid amide compounds and organic acidimide compounds. These compounds, which cleave upon exposure to theactinic rays to form an acid, may be used either singly or in anycombination thereof.

No particular limitation is imposed on the amount of these photo-inducedhardening agents blended. From the viewpoints of being able toefficiently conduct the reaction with the ring structure-containingpolymer, not impairing the physical properties of the resultingcrosslinked resin, and being profitable, however, it is generally withina range of 0.1 to 30 parts by weight, preferably 1 to 20 parts by weightper 100 parts by weight of the ring structure-containing polymer. If theamount of the photoreactive substance blended is too little, theresulting composition becomes hard to undergo crosslinking, and sosufficient heat resistance and solvent resistance cannot be imparted tothe composition. On the other hand, any amount too great results in acrosslinked resin lowered in properties such as water absorptionproperty and dielectric properties. It is hence not preferable to usethe photoreactive compound in any amount outside the above range. Theblending amount within the above range is preferred because theseproperties are balanced with each other at a high level.

Hardening Auxiliary (Curing Aid)

In the present invention, a curing aid (hardening aid) may be used forthe purpose of more enhancing curability and the dispersibility of thecompounding additives.

No particular limitation is imposed on the curing aid. Publicly knowncompounds disclosed in Japanese Patent Application Laid-Open No.34924/1987 and the like may be used. Examples thereof includeoxime.nitroso type curing aids such as quinone dioxime, benzoquinonedioxime and p-nitrosophenol; maleimide type curing aids such asN,N-m-phenylenebismaleimide; allyl type curing aids such as diallylphthalate, triallyl cyanurate and triallyl isocyanurate; methacrylatetype curing aids such as ethylene glycol dimethacrylate andtrimethylolpropane trimethacrylate; and vinyl type curing aids such asvinyltoluene, ethylvinylbenzene and divinylbenzene. Of these, the allyltype curing aids and methacrylate type curing aids are preferred becausethey are easy to be uniformly dispersed.

The amount of the curing aid blended is suitably selected according tothe kind of the hardener used. However, it is generally 0.1 to 10 partsby weight, preferably 0.2 to 5 parts by weight per part by weight of thehardener. If the amount of the curing aid blended is too little, theresulting composition becomes hard to undergo curing. On the other hand,any amount too great results in a crosslinked resin having a possibilitythat its electrical properties, moisture resistance and the like may bedeteriorated.

Other Compounding Additives

Other compounding additives may be added to the resin compositionsaccording to the present invention as needed. Examples of othercompounding additives include flame retardants, other polymer componentsand other additives.

(1) Flame Retardant

It is preferred that a flame retardant be added to the resin compositionwhen the composite film according to the present invention is used as afilm for wiring boards such as flexible printed wiring boards. Noparticular limitation is imposed on the flame retardant. However, thosewhich undergo none of decomposition, denaturation and deterioration bythe hardening agent are preferred. Halogen-containing flame retardantsare generally used.

Various kinds of chlorine- or bromine-containing flame retardants may beused as the halogen-containing flame retardants. From the viewpoints offlame proofing effect, heat resistance upon forming or molding,dispersibility in resins and influence on the physical properties of theresins, however, the following flame retardants may be preferably used.Namely, preferable examples thereof include hexabromobenzene,pentabromoethylbenzene, hexabromobiphenyl, decabromodiphenyl,hexabromodiphenyl oxide, octabromodiphenyl oxide, decabromodiphenyloxide, pentabromocyclohexane, tetrabromobisphenol A and derivativesthereof [for example, tetrabromobisphenol A-bis(hydroxyethyl ether),tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenolA-bis(bromoethyl ether), tetrabromobisphenol A-bis(allyl ether), etc.],tetrabromobisphenol S and derivative thereof [for example,tetrabromobisphenol S-bis(hydroxyethyl ether), tetrabromobisphenolS-bis(2,3-dibromopropyl ether), etc.], tetrabromophthalic anhydride andderivatives thereof [for example, tetrabromophthalimide,ethylenebistetrabromophthalimide, etc.],ethylenebis(5,6-dibromonorbornene-2,3-dicarboxyimide),tris-(2,3-dibromopropyl-1) isocyanurate, adducts ofhexachlorocyclopentadiene by Diels-Alder reaction, tribromophenylglycidyl ether, tribromophenyl acrylate, ethylenebistribromophenylether, ethylenebispentabromophenyl ether,tetradecabromodiphenoxybenzene, brominated polystyrene, brominatedpolyphenylene oxide, brominated epoxy resins, brominated polycarbonate,polypentabromobenzyl acrylate, octabromonaphthalene,hexabromocyclododecane, bis(tribromophenyl)fumaramide andN-methylhexabromodiphenylamine.

The amount of the flame retardant added is generally 3 to 150 parts byweight, preferably 10 to 140 parts by weight, particularly preferably 15to 120 parts by weight per 100 parts by weight of the ringstructure-containing polymer.

As a flame retardant auxiliary for causing the flame retardant to moreeffectively exhibit its flameproofing effect, for example, an antimonialflame retardant auxiliary such as antimony trioxide, antimony pentoxide,sodium antimonate or antimony trichloride may be used. These flameretardant auxiliaries are used in a proportion of generally 1 to 30parts by weight, preferably 2 to 20 parts by weight per 100 parts byweight of the flame retardant.

(2) Other Polymer Component

In the present invention, rubbery polymers and other thermoplasticresins may be blended into the ring structure-containing polymer, asneeded, for the purpose of imparting properties such as flexibility as afilm.

The rubbery polymers are polymers having a glass transition temperatureof ordinary temperature (25° C.) or lower and include generalrubber-like polymers and thermoplastic elastomers. The Mooney viscosity(ML₁₊₄, 100° C.) of such a rubbery polymer is suitably selected asnecessary for the end application intended and is generally 5 to 200.

Examples of the rubbery polymers include ethylene-α-olefin type rubberypolymers; ethylene-α-olefin-polyene terpolymer rubbers; copolymers ofethylene and an unsaturated carboxylic acid ester, such asethylene-methyl methacrylate copolymers and ethylene-butyl acrylatecopolymers; copolymers of ethylene and a fatty acid vinyl ester, such asethylene-vinyl acetate copolymers; polymers of acrylic acid alkyl esterssuch as ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethyl-hexylacrylate and lauryl acrylate; diene rubbers such as polybutadiene,polyisoprene, styrene-butadiene or styrene-isoprene random copolymers,acrylonitrile-butadiene copolymers, butadiene-isoprene copolymers,butadiene-alkyl (meth)acrylate copolymers, butadiene-alkyl(meth)acrylate-acrylonitrile terpolymers and butadiene-alkyl(meth)acrylate-acrylonitrile-styrene tetrapolymers; andbutylene-isoprene copolymers.

As examples of the thermoplastic elastomers, may be mentioned aromaticvinyl-conjugated diene block copolymers such as styrene-butadiene blockcopolymers, hydrogenated styrene-butadiene block copolymers,styrene-isoprene block copolymers and hydrogenated styrene-isopreneblock copolymers, low crystalline polybutadiene resins,ethylene-propylene elastomers, styrene-grafted ethylenepropyleneelastomers, thermoplastic polyester elastomers, and ethylenic ionomerresins. Of these thermoplastic elastomers, the hydrogenatedstyrene-butadiene block copolymers and hydrogenated styrene-isopreneblock copolymers are preferred. As specific examples thereof, may bementioned those described in Japanese Patent Application Laid-Open Nos.133406/1990, 305814/1990, 72512/1991 and 74409/1991, etc.

Examples of the other thermoplastic resins include low densitypolyethylene, high density polyethylene, linear low densitypolyethylene, very low density polyethylene, ethylene-ethyl acrylatecopolymers, ethylene-vinyl acetate copolymers, polystyrene,poly(phenylene sulfide), poly(phenylene ether), polyamide, polyester,polycarbonate and cellulose triacetate.

These rubbery polymers and other thermoplastic resins may be used eithersingly or in any combination thereof. The blending amount thereof issuitably selected within limits not impeding the objects of the presentinvention. However, it is preferably at most 30 parts by weight per 100parts by weight of the ring structure-containing polymer for reasons ofnot impeding the properties of the resulting insulating material.

(3) Other Additives

To the ring structure-containing polymers, may be added proper amountsof other additives such as heat stabilizers, weathering stabilizers,leveling agents, antistatic agents, slip agents, antiblocking agents,anti-fogging agents, lubricants, dyes, pigments, natural oil, syntheticoil, wax and the like as needed.

Specific examples thereof include phenolic antioxidants such astetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane,alkyl β-(3,5-di-t-butyl-4-hydroxyphenyl)propionates and2,2′-oxamidobis[ethyl-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate];phosphoric stabilizers such as trisnonylphenyl phosphite,tris(2,4-di-t-butylphenyl)phosphite andtris(2,4-di-t-butylphenyl)phosphite; fatty acid metal salts such as zincstearate, calcium stearate and calcium 12-hydroxystearate; polyhydricalcohol fatty acid esters such as glycerol monostearate, glycerolmonolaurate, glycerol distearate, pentaerythritol monostearate,pentaerythritol distearate and pentaerythritol tristearate; synthetichydrotalcite; amine type antistatic agents; leveling agents for paints,such as fluorine-containing nonionic surfactants, special acrylic resintype leveling agents and silicone type leveling agents; coupling agentssuch as silane coupling agents, titanate coupling agents,aluminum-containing coupling agents and zircoaluminate coupling agents;plasticizers; and colorants such as pigments and dyes.

These other compounding additives may be used either singly or in anycombination thereof.

The blending of the ring structure-containing polymer with variouscompounding additives may be conducted in accordance with a method knownper se in the art. Examples thereof include a method in which thecompounding additives are dissolved or dispersed in a solution with thering structure-containing polymer dissolved in a solvent to mix them, amethod in which the compounding additives are mixed with the ringstructure-containing polymer by means of a kneader such as asingle-screw or twin-screw extruder, and a method in which thecompounding additives are mixed with the ring structure-containingpolymer by means of a film extruder upon forming.

(Film (A))

The film (A) used in the present invention is a film formed from thering structure-containing polymer. The ring structure-containing polymermay be used singly, but is preferably used in the form of a resincomposition with various kinds of compounding additives such as ahardening agent mixed therewith.

No particular limitation is imposed on the forming process of the film,and the film can be formed in accordance with a method known per se inthe art. Examples of the forming process include melt extrusion andsolution casting processes.

In the case of the melt extrusion process, a film can be formed from astate of pellets by means of a film extruder or the like heretoforeused.

In the case of the solution casting (cast) process, a film is formedwith a liquid composition obtained by further adding a solvent to a ringstructure-containing polymer or a resin composition containing the ringstructure-containing polymer.

When the solvent is used, examples thereof include aromatic hydrocarbonssuch as toluene, xylene and ethylbenzene; aliphatic hydrocarbons such asn-pentane, hexane and heptane; alicyclic hydrocarbons such ascyclohexane; and halogenated hydrocarbons such as chlorobenzene,dichlorobenzene and trichlorobenzene.

The solvent is used in an amount sufficient to uniformly dissolve ordisperse the ring structure-containing polymer and the individualcomponents optionally blended therein. The amount of the solvent used isgenerally controlled in such a manner that a solids concentrationamounts to 1 to 80 wt. %, preferably 5 to 60 wt. %, more preferably 10to 50 wt. %. A curable monomer may also be used as a reactive diluent inplace of the solvent. No particular limitation is imposed on thereactive diluent so far as it is a compound which can cause a curingreaction by heat or light and is liquid at ordinary temperature.However, specific examples thereof include epoxy group-containingcompounds, (meth)acrylic acid ester compounds, vinyl ether compounds andvinyl compounds. Of these, the epoxy group-containing compounds areparticularly preferred for reasons of imparting excellent heatresistance, low water absorption property, dielectric properties and thelike.

The melt viscosity of the ring structure-containing polymer ispreferably at most 50 poises, more preferably at most 20 poises in atemperature range of 100 to 200° C. for reasons of merits in handlingand process.

The film (A) used in the present invention may be stretched afterforming.

The thickness of the film (A) used in the present invention is suitablyselected as necessary for the end application intended, but is generallywithin a range of 5 to 500 μm, preferably 10 to 300 μm, more preferably20 to 200 μm. Any film thickness falling within this range is preferredbecause the strength properties, reliability and flexibility of theresulting composite film are balanced with one another at a high level.If the thickness of the film (A) is too thin, reliability on insulationand mechanical strength of the resulting composite film are lowered. Ifthe thickness is too great, it is difficult to form minute wiring, andthe flexibility of the resulting composite film is also lowered.

The glass transition temperature (Tg) of the film (A) used in thepresent invention is suitably selected as necessary for the endapplication intended, but is generally within a range of 100 to 500° C.,preferably 130 to 400° C., more preferably 160 to 350° C. Any glasstransition temperature falling within this range is preferred becausethe properties of the resulting composite film, such as forming andprocessing ability, solder resistance and flame retardant are balancedwith one another.

The dielectric constant of the film (A) used in the present invention issuitably selected as necessary for the end application intended. Whenthe dielectric constant is generally at most 5.0, preferably at most4.0, more preferably at most 3.5, most preferably at most 3.0 asmeasured at 1 MHz, however, the properties of the resulting compositefilm, such as reliability on insulation and speeding-up ability as acircuit board become far excellent. Therefore, it is preferable to use afilm having such a dielectric constant.

The dielectric loss tangent of the film (A) used in the presentinvention is suitably selected as necessary for the end applicationintended. When the dielectric loss tangent is generally at most 0.10,preferably at most 0.05, more preferably at most 0.01 as measured at 1MHz, however, the properties of the resulting composite film, such ashigh-frequency properties and low transmission loss as a circuit boardbecome far excellent. Therefore, it is preferable to use a film havingsuch a dielectric loss tangent.

The water absorptivity of the film (A) used in the present invention issuitably selected as necessary for the end application intended. Whenthe water absorptivity is generally at most 0.50%, preferably at most0.10%, more preferably at most 0.05%, however, the properties of theresulting composite film, such as solder resistance and resistance toion migration become excellent. Therefore, it is preferable to use afilm having such a water absorptivity.

When the film (A) used in the present invention is formed from a curableresin composition comprising the ring structure-containing polymer andthe hardening agent, the film may be cured (crosslinked) by heating orexposure to light during or after the formation of the film, or afterthe formation of a composite film.

Film (B) Formed from Polycondensation Polymer

(Polycondensation Polymer)

No particular limitation is imposed on the polycondensation polymer usedin the present invention, and any industrially generally known polymermay be used. Specific examples thereof include polyether resins such aspoly(phenylene ether), poly(phenylene oxide); thermoplastic polyesterresins such as polyethylene terephthalate, polybutylene terephthalateand liquid crystal polyester; polyamide resins; and polyimide resins. Ofthese, the polyester resins and polyimide resins are preferred from theviewpoints of mechanical strength, heat resistance, etc. Further, theliquid crystal polyester resin and polyimide resins are more preferredfrom the viewpoints of flame retardant and the like, with the polyimideresins being particularly preferred in that they have high mechanicalstrength, heat resistance and flame retardant.

When an aromatic ring is present in the polycondensation polymer, theadaptability of the film, such as adhesion property to the ringstructure-containing polymer film (A) and various physical properties(elongation, coefficient of linear expansion and molding shrinkage) areimproved. Therefore, it is pertinent to control the content of themonomer unit having an aromatic ring in the polycondensation polymer becontrolled to at least 10 wt. %, preferably at least 30 wt. %, morepreferably at least 50 wt. %.

A preferred polyimide resin in the present invention is a resinsynthesized from a tetracarboxylic acid dianhydride and a diamine bothhaving an aromatic ring. This resin is far excellent in mechanicalstrength and heat resistance. The polyimide resins also includepolyamide-imide resins obtained by the reaction of an aromatictricarboxylic acid anhydride with an aromatic diamine in addition tosuch condensation type overall aromatic polyimide resins.

When examples of preferred polyimide resins are mentioned as combinationof a tetracarboxylic acid dianhydride and a diamine, there may bementioned, for example, polycondensation products of pyromellitic aciddianhydride (PMDA) and oxydianiline (ODA); polycondensation products ofbiphenyltetracarboxylic acid dianhydride (BTDA) and p-phenylenediamine(PPD); and polycondensation products of benzophenonetetracarboxylic aciddianhydride (BTDA) and benzophenonediamine (BDA). Of these, thepolycondensation products of BTDA and PPD are most preferred in thatthey are excellent in heat resistance and mechanical strength. Apolyimide resin is generally formed into a film by forming a film with aprecursor (polyamic acid) thereof and then cyclodehydrating the polyamicacid to imidate it.

The solution viscosity of the polycondensation polymer is generally atleast 0.05 dl/g, preferably at least 0.1 dl/g in terms of inherentviscosity η_(inh) at 30° C. in dimethylformamide (DMF). When thesolution viscosity of the polycondensation polymer falls within thisrange, the mechanical strength and film-forming property of the polymerare well balanced with each other. It is hence preferred to use apolycondensation polymer having a solution viscosity within this range.

These polycondensation polymers may be used either singly or in anycombination thereof.

The film (B) used in the present invention may contain various kinds ofcompounding additives, as needed, in addition to the polycondensationpolymer. Namely, the film (B) may be formed from a resin composition.The kinds, blending proportions and mixing method of the compoundingadditives are the same as those in the case of the film (A).

The film (B) used in the present invention is obtained by forming thepolycondensation polymer or the resin composition comprising thepolycondensation polymer and the compounding additives. The film can beformed in accordance with a method known per se in the art, and theprocess thereof is the same as in the case of the film (A). However,when the film is formed through a precursor of the polymer like thepolyimide resin, for example, an imidation reaction by cyclodehydrationof polyamic acid is required.

The thickness of the film (B) used in the present invention is suitablyselected as necessary for the end application intended, but is generallywithin a range of 5 to 500 μm, preferably 10 to 300 μm, more preferably20 to 200 μm. Any film thickness falling within this range is preferredbecause the strength properties, reliability and flexibility of the filmare balanced with one another at a high level. If the thickness of thefilm (B) is too thin, reliability on insulation and mechanical strengthof the film are lowered. If the thickness is too great, it is difficultto form minute wiring, and the flexibility of the film is also lowered.

The glass transition temperature (Tg) of the film (B) used in thepresent invention is suitably selected as necessary for the endapplication intended, but is generally within a range of 100 to 500° C.,preferably 150 to 400° C., more preferably 200 to 350° C. Any glasstransition temperature falling within this range is preferred becausethe reliability and forming and processing ability of the resultingcomposite film are balanced with each other.

The dielectric constant of the film (B) used in the present invention issuitably selected as necessary for the end application intended, but itis generally at most 5.0, preferably at most 4.0, more preferably atmost 3.5 as measured at 1 MHz.

The dielectric loss tangent of the film (B) used in the presentinvention is suitably selected as necessary for the end applicationintended, but it is generally within a range of 0.005 to 0.03,preferably 0.001 to 0.02, more preferably 0.002 to 0.01 as measured at 1MHz.

The tensile strength of the film (B) used in the present invention issuitably selected as necessary for the end application intended, but isgenerally within a range of 100 to 400 MPa, preferably 150 to 300 MPa,more preferably 200 to 250 MPa.

The elastic modulus of the film (B) used in the present invention issuitably selected as necessary for the end application intended, but isgenerally within a range of 1.5 to 10 GPa, preferably 2.0 to 9 GPa, morepreferably 3.0 to 8 GPa.

The elongation of the film (B) used in the present invention is suitablyselected as necessary for the end application intended, but is generallywithin a range of 30 to 150%, preferably 40 to 120%, more preferably 50to 100%.

The water absorptivity of the film (B) used in the present invention issuitably selected as necessary for the end application intended, but itis generally within a range of 0.1 to 0.5%, preferably 0.2 to 0.4%, morepreferably 0.25 to 0.35%.

(Composite Film)

The composite film according to the present invention is a multi-layerfilm having a layer structure of at least two layers, wherein the ringstructure-containing polymer film (A) and the polycondensation polymerfilm (B) adjoin each other directly or through an adhesive layer.

No particular limitation is imposed on the layer structure of thecomposite film according to the present invention, and examples thereofinclude (A)/(B), (A)/(B)/(A), (B)/(A)/(B), (A)/(B)/(A)/(B),(A)/(B)/(A)/(B)/(A) and (B)/(A)/(B)/(A)/(B). The number of layers may beincreased more than this as needed. However, the number of layers isgenerally at most 10 layers, preferably at most 7 layers, morepreferably at most 5 layers in total from the viewpoints of flexibilityand profitability. In many cases, good results can be achieved by 2 or 3layers.

The composite films may be classified by the layer structure and whichside the film (A) or (B) is arranged on. There are composite filmshaving a layer structure that these two kinds of films are containedmore than 2 layers in total, and the film (A) or (B) is arranged on eachside. Specific examples thereof include (A)/(B)/(A),(A)/(B)/(A)/(B)/(A), (B)/(A)/(B) and (B)/(A)/(B)/(A)/(B).

There are composite films having a layer structure that these two kindsof films are contained more than 1 layer in total, the film (A) isarranged on one side thereof, and the film (B) is arranged on the otherside. Specific examples thereof include (A)/(B) and (A)/(B)/(A)/(B).

Of these, composite films at least one side of which is composed of thefilm (A) are preferred in the application fields of which low absorptionproperty is particularly required, with composite films both sides ofwhich are composed of the film (A) being particularly preferred. On theother hand, composite films at least one side of which is composed ofthe film (B) are preferred in the application fields of which flameretardant is particularly required, with composite films both sides ofwhich are composed of the film (B) being particularly preferred.

Processes for forming a composite film (multi-layer film) from the films(A) and (B) is not limited to particular processes. Typical processesthereof will hereinafter be described.

A first process is a process in which the film (A) preformed is used asa support, a solution of the polycondensation polymer (or a precursorthereof) which is a material for the film (B) is applied to the surfaceof the support, and the solution is then dried and completely cured asneeded to form a composite film. When the film (A) contains a hardeningagent, it may be cured at the same time as the curing of the film (B).

A second process is a process in which the film (B) preformed is used asa support, a solution of the ring structure-containing polymer which isa material for the film (A) is applied to the surface of the support,and the solution is then dried to form a composite film. When the ringstructure-containing polymer is provided as a resin compositioncomprising a hardening agent, it may be cured (crosslinked) by a heattreatment or exposure to light after drying.

A third process is a process in which the films (A) and (B) preformedare laminated on each other and fusion-bonded to each other underpressure by means of a hot press or the like. In this case, when thefilm (A) contains a hardening agent, similarly it may be cured at thesame time as the fusion bonding under pressure or after the fusionbonding under pressure.

A fourth process is a process in which the films (A) and (B) preformedare bonded to each other through an adhesive layer. The adhesive layeris formed by applying an adhesive to the surface of at least one film orby interposing an adhesive film between both films.

A fifth process is a process in which polymers for both films areco-extruded from an extruder to form a composite film when thepolycondensation polymer is a thermoplastic resin. In this case, anadhesive layer may also be co-extruded.

These processes are carried out either singly or successively, whereby amulti-layer film of at least two layers can be formed.

Among the above-described processes, the first and second processes areparticularly preferred because the formation of the respective films (A)and (B), and the formation of the multi-layer film can be conducted atthe same time, and the process is simple.

The thickness of the composite film according to the present inventionis suitably selected as necessary for the end application intended, butis generally within a range of 10 to 800 μm, preferably 15 to 500 μm,more preferably 20 to 300 μm. Any film thickness falling within thisrange is preferred because the strength properties, reliability andflexibility of the composite film are balanced with one another at ahigh level.

The thickness ratio of the film (A) to the film (B) in the compositefilms according to the present invention is suitably selected asnecessary for the end application intended. When the thickness ratio isgenerally within a range of 99:1 to 1:99, preferably 90:10 to 10:90,more preferably 80:20 to 20:80, however, the mechanical strength,flexibility, low water absorption property and flame retardant of such acomposite film are balanced with one another at a high level. It ishence preferable for the thickness ratio to fall within this range.

The fundamental physical properties of the composite films according tothe present invention are as follows:

(i) the dielectric constant as measured at 1 MHz is generally 2.3 to3.0, preferably 2.5 to 2.8;

(ii) the dielectric loss tangent as measured at 1 MHz is generally 0.005to 0.03, preferably 0.01 to 0.02;

(iii) the water absorptivity as determined under conditions of atemperature of 85° C., a relative humidity of 85% and measuring time of300 hours is generally 0.05 to 0.3%, preferably 0.07 to 0.2%, morepreferably 0.08 to 0.15%;

(iv) the tensile strength is generally 50 to 400 MPa, preferably 100 to300 MPa, more preferably 150 to 200 MPa;

(v) the elastic modulus is generally 1.5 to 10 GPa, preferably 2.0 to 9GPa, more preferably 3.0 to 8 GPa; and

(vi) the tensile elongation is generally 10 to 100%, preferably 30 to80%, more preferably 40 to 60%.

The composite films according to the present invention preferably haveat least one of the above-described physical properties, more preferablythe physical properties (i) to (iv), most preferably all the physicalproperties.

The composite films according to the present invention preferablyexhibit flame retardant of V-0 in accordance with the UL standard.

(Conductive Layer)

The composite film according to the present invention is suitable foruse as a film for wiring boards. When it is used in this applicationfield, a conductive layer is generally formed on at least one sidethereof.

The conductive layer formed on the composite film in the presentinvention is composed of a layer of a metal such as copper. Morespecifically, the conductive layer may be formed by a method oflaminating a metal foil such as copper foil (electrolytic copper foil orrolled copper foil) on the surface of the composite film, a method ofplating the surface of the composite film with a metal, a method offorming a metal film on the surface of the composite film by sputtering,or the like. When the composite film is used as a film for wiringboards, it is used in a state that a wiring pattern has been formedthereon.

An example of a process for forming a wiring pattern includes a processcomprising forming a metal foil layer composed of copper or the like asa conductive layer on the composite film, forming a resist pattern by aphotolithographic method making use of a mask pattern, and removingunnecessary portions of the metal foil layer by etching to form a wiringpattern. Besides, a wiring pattern may also be formed on the compositefilm by sputtering or plating.

The thickness of the conductive layer is generally 1 to 100 μm,preferably 5 to 30 μm, more preferably 10 to 20 μm. When the thicknessof the conductive layer falls within the above range, both properties ofreliability and minute processing ability are balanced with each otherat a high level. It is hence preferable for the thickness to fall withinthis range.

The composite film on which the wiring pattern has been formed is usefulin an application field of a film for wiring boards in flexible printedwiring boards, carrier films of semiconductor packages, wiring boardsfor semiconductor chip mounting, etc.

As more specific uses, they may be used in a great number of applicationfields as flexible printed circuit boards (FPC) for connecting printedboards used in potable information apparatus such as electronicpocketbooks, personal computers, potable telephones and PHS, and imageprocessing apparatus such as digital cameras and camcoders; tapes fortape automated bonding (TAB); carrier films and base films for tapecarrier packages (TCP), chip size packages (CSP) and the like assemiconductor packages; high-density multi-layer interconnection layersfor packages such as multi-chip module and ballbrid array; etc.

Examples of specific forms of CSP include μ-BGA, FBGA, FLGA, SON, SOLand mold CSP. The carrier film or base film is provided between layersof a semiconductor chip and a connecting member (lead, bump, etc.) as aninsulating film for each of the above-described packages.

EXAMPLES

The present invention will hereinafter be described more specifically bythe following Synthesis Examples, Examples and Comparative Examples. Alldesignations of “part” or “parts” as will be used in these examples andthe like mean part or parts by weight.

[Testing and Evaluating Methods]

(1) The glass transition temperature (Tg) was measured in accordancewith the differential scanning calorimetry (DSC method).

(2) The molecular weight was determined in terms of polystyrene asmeasured by gel permeation chromatography (GPC) using toluene as asolvent unless expressly noted.

(3) The rate of hydrogenation in a main chain and the modification rateof a polymer were determined by ¹H-NMR.

(4) The dielectric constant and dielectric loss tangent at 1 MHz weredetermined in accordance with JIS C 6481.

(5) The flexural strength, tensile strength and tensile elongation at anordinary temperature, and the water absorptivity under conditions of atemperature of 85° C., RH of 85% and measuring time of 300 hours weredetermined in accordance with JIS K 6911.

(6) A temperature cycle test (TCT) was conducted by repeating atemperature cycle of “−55° C. (30 min)→room temperature (5 min)→150° C.(30 min)→room temperature (5 min)” 500 times to apply temperature shockto a composite film sample, thereby investigating whether crackingoccurred or not.

(7) A pressure cooker test (PCT) was conducted by leaving a compositefilm sample to stand for 300 hours under an environment of 100% inhumidity and 105° C. to investigate whether failure occurred or not.

Synthesis Example 1 Synthetic Example of Ring Structure-containingPolymer

Tungsten hexachloride, triisobutylaluminum and isobutyl alcohol wereused as a polymerization catalyst to polymerize8-ethyltetracyclo[4.4.1^(2,5).1^(7,10).0]-dodec-3-ene (i.e.,ethyltetracyclododecene; hereinafter abbreviated as ETD) in accordancewith a publicly known process. The thus-obtained ring-opening polymerwas hydrogenated using nickel acetylacetonate and triisobutylaluminum ashydrogenation catalyst in accordance with a publicly known process toobtain a hydrogenated product of the ring-opening polymer of ETD(hydrogenation rate≧99%, Tg=138° C., Mn=18,500, Mw=31,600).

With 100 parts of the hydrogenated product were mixed 30 parts of maleicanhydride, 10 parts of dicumyl peroxide and 300 parts oftert-butylbenzene to conduct a graft modification reaction at 150° C.for 4 hours in an autoclave. The reaction mixture thus obtained was thensolidified, and the solidified product was dried to obtain a maleicanhydride-modified polymer (a1). The modified polymer (a1) thus obtainedhad Tg of 166° C., Mn of 16,400, Mw of 35,200 and a modification rate of28%.

When 15 parts of the modified polymer (a1) and 0.6 parts of4,4′-bisazidobenzal(4-methyl)cyclohexane as a crosslinking agent weredissolved in 45 parts of xylene, a uniform solution was provided withoutforming any precipitate.

Synthesis Example 2 Synthetic Example of Ring Structure-containingPolymer

An epoxy-modified polymer (a2) was obtained in the same manner as inSynthesis Example 1 except that 30 parts of maleic anhydride werechanged to 30 parts of allyl glycidyl ether. The modified polymer (a2)thus obtained had Tg of 160° C., Mn of 17,100, Mw of 36,900 and amodification rate of 24%.

When 15 parts of the modified polymer (a2) and 0.6 parts of4,4′-bisazidobenzal(4-methyl)cyclohexane as a crosslinking agent weredissolved in 45 parts of xylene, a uniform solution was provided withoutforming any precipitate.

Synthesis Example 3 Synthetic Example of Ring Structure-containingPolymer

A glass container purged with nitrogen was charged with 150 parts oftoluene, 50 parts of a 67% toluene solution of 2-norbornene (hereinafterabbreviated as NB) and 35 parts of 5-decyl-2-norbornene (hereinafterabbreviated as DNB). Then, 10 parts of a toluene solution (2.5 mmol/l)of nickel acetylacetonate and 10 parts of a toluene solution (500mmol/l) of ethylaluminum dichloride were added to conduct apolymerization reaction at 50° C. for 5 hours. After completion of thereaction, the reaction mixture was poured into a large amount ofmethanol to deposit a polymer formed. The polymer was collected byfiltration, washed and then dried under reduced pressure, therebyobtaining 45 parts of an addition copolymer. The addition copolymer hadMn of 69,200, Mw of 132,100, a compositional ratio NB/DNB of monomers of76/24 (molar ratio) and Tg of 270° C.

Dissolved in 130 parts of t-butylbenzene were 28 parts of the additioncopolymer obtained above, 10 parts of 5,6-epoxy-1-hexene and 2 parts ofdicumyl peroxide, and a graft modification reaction was conducted at140° C. for 6 hours. The thus-obtained solution of a reaction productwas poured into 300 parts of methanol to solidify the reaction product.The epoxy-modified polymer thus solidified was dried under vacuum at100° C. for 20 hours, thereby obtaining 26 parts of an epoxy-modifiednorbornene polymer (a3). This modified polymer had Mn of 72,600, Mw of141,400 and Tg of 275° C. The epoxy group content in the modifiedpolymer was 7.4% per repeating structural unit of the polymer asmeasured by ¹H-NMR.

When 15 parts of the modified polymer (a3) and 0.6 parts of4,4′-bisazidobenzal(4-methyl)cyclohexane as a crosslinking agent weredissolved in 45 parts of xylene, a uniform solution was provided withoutforming any precipitate.

Example 1

A solution of the maleic anhydride-modified polymer (a1) obtained inSynthesis Example 1 was applied on to a conventional polyimide film(Eupilex Film, product of Ube Industries, Ltd.; thickness: 50 μm) forflexible printed boards by means of a spin coater and then heated at 80°C. for 15 minutes to remove the solvent and dry the solution, therebyforming a coating film of the maleic anhydride-modified polymer (a1)having a thickness of 50 μm.

After an electrolytic copper foil having a thickness of 18 μm waspress-bonded under heating on to the coating film of the maleicanhydride-modified polymer (a1) at 250° C. for 5 minutes, the coatingfilm was heated at 170° C. for 4 hours to completely cure the resin,thereby forming a composite film having a conductive layer.

A resist film was formed on the conductive layer of the thus-obtainedcomposite film having the conductive layer using a photolithographicmethod. After the resist film was exposed on a pattern through aphotomask and developed, unnecessary portions of the copper foil wereremoved with an etching agent to form a wiring pattern. The propertiesof the composite film on which the wiring pattern had been formed wereevaluated. The results were as follows:

water absorptivity=0.175%;

dielectric constant=2.8;

dielectric loss tangent=0.0035;

tensile strength=180 MPa; and

flame retardant=V-0 (UL standard).

(Production of Tape Carrier Package, TCP)

A semiconductor chip was mounted on the composite film, on which thewiring pattern had been formed, by bare chip bonding through a lead, anda TCT test and a PCT test were performed thereon to determine percentdefective. As a result, it was at most 5% in each test.

Example 2

Evaluation was conducted in the same manner as in Example 1 except thata solution of the epoxy-modified polymer (a2) obtained in SynthesisExample 2 was used. As a result, the properties of the composite filmwere found to be as follows:

water absorptivity=0.173%;

dielectric constant=2.75;

dielectric loss tangent=0.0033;

tensile strength=183 MPa; and

flame retardant=V-0 (UL standard).

Similarly, the results (percent defective) of both TCT test and PCT teston the composite film were also found to be at most 5%.

Example 3

Evaluation was conducted in the same manner as in Example 1 except thata solution of the epoxy-modified polymer (a3) obtained in SynthesisExample 3 was used. As a result, the properties of the composite filmwere found to be as follows:

water absorptivity=0.170%;

dielectric constant=2.70;

dielectric loss tangent=0.0032;

tensile strength=175 MPa; and

flame retardant=V-0 (UL standard).

Similarly, the results (percent defective) of both TCT test and PCT teston the composite film were also found to be at most 5%.

Comparative Example 1

Evaluation was conducted by using a single polyimide film (Eupilex Film)having a thickness of 100 μm in place of the composite film used inExample 1. As a result, the properties of the film were found to be asfollows:

water absorptivity 0.30%;

dielectric constant=3.2;

dielectric loss tangent=0.03;

tensile strength=300 MPa; and

flame retardant=V-0 (UL standard).

The result (percent defective) of the TCT test on the film was found tobe at most 5%, but the result (percent defective) of the PCT test wasfound to be as high as 12%.

Example 4

A solution of the maleic anhydride-modified polymer (a1) obtained inSynthesis Example 1 was applied on to a conventional polyimide base film(thickness: 25 μm) for LOC (lead on chip) packaging tapes by means of aspin coater and then heated at 80° C. for 15 minutes to remove thesolvent and dry the solution, thereby forming a coating film of themaleic anhydride-modified polymer (a1) having a thickness of 25 μm. Thecoating film of the maleic anhydride-modified polymer (a1) was heated at170° C. for 4 hours to completely cure the resin, thereby forming acomposite film.

The properties of the composite film thus obtained were evaluated. Theresults were as follows:

water absorptivity=0.175%;

dielectric constant=2.8; and

dielectric loss tangent=0.0035.

(Production of LOC Package)

The above-obtained composite film was sandwiched between a lead and asemiconductor chip to bond them to each other, thereby producing a LOCpackage (a sort of CSP). A TCT test and a PCT test were carried out onthe package to determine percent defective. As a result, it was at most5% in each test.

Comparative Example 2

A LOC package was produced in the same manner as in Example 4 exceptthat a single polyimide base film (thickness: 50 μm; Eupilex Film) wasused in place of the composite film, thereby evaluating it. As a result,it was found that the percent defective in the TCT test was at most 5%,the percent defective in the PCT test was 14%, and the flame retardantwas V-0 in accordance with the UL standard.

Comparative Example 3

A solution of the maleic anhydride-modified polymer (a1) obtained inSynthesis Example 1 was applied on to a silicon wafer by means of a spincoater and then heated at 80° C. for 15 minutes to remove the solventand dry the solution, thereby forming a coating film of the maleicanhydride-modified polymer (a1) having a thickness of 100

After an electrolytic copper foil having a thickness of 18 μm waspress-bonded under heating on to the coating film at 250° C. for 5minutes, the coating film of the polymer was heated at 170° C. for 4hours to completely cure the resin. The coating film was then peeledfrom the silicon wafer to form a film having a conductive layer.

A resist film was formed on the conductive layer of the thus-obtainedfilm having the conductive layer using a photolithographic method. Afterthe resist film was exposed on a pattern through a photomask anddeveloped, unnecessary portions of the copper foil were removed with anetching agent to form a wiring pattern. The properties of the film onwhich the wiring pattern had been formed were evaluated. The resultswere as follows:

water absorptivity=0.05%;

dielectric constant=2.4;

dielectric loss tangent=0.0007;

tensile strength=50 MPa; and

flame retardant=HB (UL standard).

From the comparison of the above-descried Examples with the ComparativeExamples, it was confirmed that the composite films according to thepresent invention are excellent in balance among low water absorptionproperty, dielectric properties and mechanical strength, and reliabilityof the flexible printed wiring boards and semiconductor packagesproduced with such a composite film is also excellent.

INDUSTRIAL APPLICABILITY

According to the present invention, there are provided composite filmsexcellent in balance among low water absorption property, dielectricproperties and mechanical strength. According to the present invention,there are also provided flexible printed wiring boards and wiring filmsfor semiconductor packages, which are produced with such a compositefilm and excellent in reliability on both TCT test and PCT test, andfurther semiconductor packages using such a wiring film.

What is claimed is:
 1. A composite film having a layer structure of atleast two layers, wherein a film layer (A) formed from a resincomposition comprising a ring structure-containing polymer comprising arepeating unit derived from ring-opening or addition polymerization of amonomer having a ring structure, and a hardening agent, and a film layer(B) formed from a polycondensation polymer selected from the groupconsisting of polyether resin, thermoplastic polyester resin, polyamideresin and polyimide resin adjoin each other directly or through anadhesive layer.
 2. The composite film according to claim 1, wherein thering structure-containing polymer is at least one (co)polymer selectedfrom the group consisting of: (a) a ring-opening or addition (co)polymerof a norbornene monomer; (b) an addition (co)polymer of a monocycliccycloolefin monomer; (c) an addition (co)polymer of a cyclic conjugateddiene monomer; (d) an addition (co)polymer of a vinyl cyclichydrocarbon; and (e) a modified product of any one of these(co)polymers.
 3. The composite film according to claim 2, wherein thering-opening or addition (co)polymer of the norbornene monomer is atleast one norbornene polymer selected from the group consisting of: (1)a ring-opening (co)polymer of the norbornene monomer; (2) an addition(co)polymer of the norbornene monomer; and (3) an addition copolymer ofthe norbornene monomer with another monomer copolymerizable with thenorbornene monomer.
 4. The composite film according to claim 1, whereinthe ring structure-containing polymer comprises a monomer having anorganic group having at least 2 carbon atoms in its side chain.
 5. Thecomposite film according to claim 2, wherein the modified product (e) ofthe (co)polymer is obtained by modifying each of the polymers (a) to (d)by a modification reaction selected from the group consisting of:{circle around (1)} a hydrogenation reaction of carbon-carbonunsaturated bonds; {circle around (2)} a graft reaction of a functionalgroup-containing unsaturated compound; {circle around (3+L )} a reactionfor introducing a functional group by direct modification of acarbon-carbon unsaturated bond; and {circle around (4)} combinations ofthese reactions.
 6. The composite film according to claim 2, wherein thering structure-containing polymer is at least one thermoplasticnorbornene resin selected from the group consisting of the ring-openingor addition (co)polymer (a) of the norbornene monomer and modifiedproducts thereof.
 7. The composite film according to claim 6, whereinthe thermoplastic norbornene resin is at least one selected from thegroup consisting of norbornene polymers having a polar group as afunctional group, and modified products obtained by introducing a polargroup into the ring-opening or addition (co)polymer (a) of thenorbornene monomer by a modification reaction.
 8. The composite filmaccording to claim 1, wherein the hardening agent is an organicperoxide, a hardening agent exhibiting its effect by heat, or ahardening agent exhibiting its effect by light.
 9. The composite filmaccording to claim 1, wherein the film (A) is a film formed from a resincomposition containing a flame retardant in addition to the ringstructure-containing polymer and the hardening agent.
 10. The compositefilm according to claim 1, wherein the composite film is a compositefilm containing at least two layers of the film layer (A) or the filmlayer (B) and having a layer structure wherein the film layer (A) or thefilm layer (B) is arranged on both sides thereof.
 11. The composite filmaccording to claim 10, which has a layer structure of (A)/(B)/(A),(A)/(B)/(A)/(B)/(A), (B)/(A)/(B) or (B)/(A)/(B)/(A)/(B).
 12. Thecomposite film according to claim 1, wherein the composite film is acomposite film having a layer structure wherein the film layer (A) isarranged on one side thereof, and the film layer (B) is arranged on theother side.
 13. The composite film according to claim 12, which has alayer structure of (A)/(B) or (A)/(B)/(A)/(B).
 14. The composite filmaccording to claim 1, wherein the composite film has at least onephysical property selected from the group consisting of: (i) adielectric constant as measured at 1 MHz of 2.3 to 3.0; (ii) adielectric loss tangent as measured at 1 MHz of 0.005 to 0.03; (iii) awater absorptivity as determined under conditions of a temperature of85° C., a relative humidity of 85% and measuring time of 300 hours of0.05 to 0.3%; and (iv) a tensile strength of 50 to 400 MPa.
 15. Thecomposite film according to claim 1, wherein the ringstructure-containing polymer is a thermoplastic norbornene resin, andthe polycondensation polymer is a polyimide resin.
 16. The compositefilm according to claim 1, further comprising a conductive layer on atleast one side of the composite film.
 17. The composite film accordingto claim 16, wherein the conductive layer is formed on at least one sideof the composite film by lamination of a metal foil, plating with ametal or sputtering of a metal.
 18. The composite film according toclaim 17, wherein a wiring pattern is formed in the conductive layer.19. The composite film according to claim 1, wherein the composite filmis a film for wiring board.
 20. The composite film according to claim19, wherein the wiring board is a wiring board for a semiconductorpackage, flexible printed wiring board or wiring board for semiconductorchip mounting.
 21. A composite film having a layer structure of at leasttwo layers, wherein a film layer (A) formed from a ringstructure-containing polymer, which comprises a repeating unit derivedfrom ring-opening polymerization of a monomer having a ring structure,carbon-carbon double bonds present in the main chain of which aresaturated by hydrogenation, and in which a function group is introducedin a proportion of 1 to 30 mol % based on the repeating unit in thepolymer, and a film layer (B) formed from a polycondensation polymerselected from the group consisting of polyether resin, thermoplasticpolyester resin, polyamide resin and polyimide resin adjoin each otherdirectly or through an adhesive layer.
 22. A composite film having alayer structure of at least two layers, wherein a film layer (A) formedfrom a ring structure-containing polymer comprising a repeating unitderived from addition polymerization of a monomer having a ringstructure, and a film layer (B) formed from a polycondensation polymerselected from the group consisting of polyether resin, thermoplasticpolyester resin polyamide resin and polyimide resin adjoin each otherdirectly or through an adhesive layer.